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Abstract

Transformation optics provides a promising way to guide waves in the open space. It is shown that a small waveguide coated with transformation medium will behave as a big virtual tunnel connecting two waveguide ports separated faraway. The waves are transmitted and guided smoothly in the open space through this ‘invisible tunnel’. The transformation medium is obtained by squeezing the space between the two ports into a small region. Numerical simulations are performed to illustrate this idea.

Figures (4)

(a) Schematic of a waveguide in free space whose two ports A and B are far away from each other. (b) With the transformation medium, we can build an invisible tunnel between the two ports to transmit waves in the open space. The dashed sphere with radius D denotes the original space before transformation, and the dark blue sphere with radius R1 represents the transformed space. The light blue annulus region is designed to meet the impedance matching requirement.

(a) Electric field distribution when the TE polarized wave is transmitted by the 2D waveguide (b) Two waveguide ports placed face to face. The EM wave is transmitted from the left port and a large portion of the energy is dispersed in the open space. (c) Electric field distribution of the system when a small waveguide coated with a transformation medium is placed between the two open waveguide ports, behaving as a large invisible tunnel connecting the two ports.

(a) Field distribution when a small waveguide coated with transformation medium is placed between two big waveguide ports which are separated faraway. (b) Field distribution of the above case when the transformation medium is shifted to the side of the waveguides ports.

The electric field distribution of the case where a small bent waveguide (0.02m wide) coated with transformation medium works as a tunnel connecting two orthogonally located waveguide ports (0.2m wide).